CVE-2021-21309 Information

Description

Redis is an open-source in-memory database that persists on disk. In affected versions of Redis an integer overflow bug in 32-bit Redis version 4.0 or newer could be exploited to corrupt the heap and potentially result with remote code execution. Redis 4.0 or newer uses a configurable limit for the maximum supported bulk input size. By default it is 512MB which is a safe value for all platforms. If the limit is significantly increased receiving a large request from a client may trigger several integer overflow scenarios which would result with buffer overflow and heap corruption. We believe this could in certain conditions be exploited for remote code execution. By default authenticated Redis users have access to all configuration parameters and can therefore use the “CONFIG SET proto-max-bulk-len” to change the safe default making the system vulnerable. This problem only affects 32-bit Redis (on a 32-bit system or as a 32-bit executable running on a 64-bit system). The problem is fixed in version 6.2 and the fix is back ported to 6.0.11 and 5.0.11. Make sure you use one of these versions if you are running 32-bit Redis. An additional workaround to mitigate the problem without patching the redis-server executable is to prevent clients from directly executing CONFIG SET: Using Redis 6.0 or newer ACL configuration can be used to block the command. Using older versions the rename-command configuration directive can be used to rename the command to a random string unknown to users rendering it inaccessible. Please note that this workaround may have an additional impact on users or operational systems that expect CONFIG SET to behave in certain ways.

CVSS Vector

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Reference

https://github.com/redis/redis/commit/c992857618db99776917f10bf4f2345a5fdc78b0 https://github.com/redis/redis/security/advisories/GHSA-hgj8-vff2-7cjf https://github.com/redis/redis/pull/8522 https://security.gentoo.org/glsa/202103-02

Attack Complexity

LOW

Privileges Required

LOW

User Interaction Required

LOW

Scope

NONE

Confidentiality Impact

UNCHANGED

Integrity Impact

HIGH

Availability Impact

HIGH

Base Score

HIGH

Base Severity

8.8